This invention relates to a seat belt system for an automotive vehicle, and more particularly relates to an improved structure for slidably mounting onto a guide rail a slider connected with the upper end of a shoulder belt.
FIG. 1 illustrates a conventional seat belt system in which a shoulder belt is automatically locked on a passenger or driver. A front seat 1 is arranged in the vehicle body. A shoulder belt 2 provided near the front seat 1 has one end which is connected through a retractor 3 with a floor 4 of the vehicle body and the other end which is connected with a slide block or slider 5. The slider 5 is slidably guided by a guide rail 6 fixed to a roof side rail 7. An anchoring device 8 is positioned at the rear end of the guide rail 6. An actuating wire 9 is connected at its one end with the engaging portion of the slider 5 for pushing and pulling it when it is actuated by a motor 10 in response to the opening and closing of a door. That is, when the door is opened, the slider 5 moves forwards so as to permit the driver or passenger to sit on the seat, and when it is closed, the slider 5 moves backwards so as to tighten the seat belt automatically on the driver or passenger.
As shown in FIG. 2, the guide rail 6 is formed in a channel shape so as to facilitate the fitting of it to the roof side rail 7. The base portion 6a of the guide rail 6 is directly fixed on the roof side rail 7 while the engaging portion 6b thereof protrudes into the passenger compartment. The open side of the engaging portion 6b faces the passenger compartment. The engaging portion 5' of the slider 5 engages the engaging portion 6b of the guide rail 6. When the force is exerted on the slider 5 in the direction denoted by the arrow F, the slider 5 is mainly supported by the flange portion 6c formed at the lower edge of the guide rail 6. The flange portion 6c of the guide rail 6 is apt to deform so that the slider 5 jumps or gets off the guide rail 6.
In order to prevent the slider 5 from getting off the guide rail 6, the height H of the flange portion 6c may be set large. However, it results in the enlargement of the inner height C of the guide rail 6.
When the force is exerted on the slider 5 in the direction F', the shearing load is given to the inward edge G.sub.1 of the neck portion of the engaging portion 5' of the slider 5. Thus, the width D of the engaging portion 5' of the slider 5 must be enlarged.
The section of the guide rail 6 and the slider 5 must be enlarged in order to obtain a reinforced structure whereby the slider 5 does not get off the guide rail 6. This causes the space of the passenger compartment to become small or restricted so that the driver and/or passengers can not comfortably enter into and sit in the compartment. Thus, such a reinforced structure can be arranged only in the vehicle body having a larger size of roof side rail.
The height C and width E of the guide rail 6 must be carefully set accurate so as to actuate smoothly the slider 5. However, if the guide rail 6 is formed along the curved inside wall of the vehicle body, the height C and the width E of the guide rail 6 are often not accurate. Therefore, the guide rail 6 must be straight in order to avoid such a problem.
Also, because it is dangerous if the engaging portion 5' of the slider 5 is exposed, the engaging portion 5' of the slider 5 is usually covered by a trim cover 11 as shown in FIG. 3. In such a case, a bracket 12 must be additionally provided to fit the trim cover 11 to the guide 6 or the roof side rail 7. This causes the production cost and the weight of the vehicle body to increase.
In order to improve the workability of the slider 5, a roller 13 may be provided as the engaging portion 5' of the slider 5 engaging with the guide rail 6 as shown in FIGS. 4A and 4B. In such a case, the slider 5 easily gets off the guide rail 6 because the contact area of the engaging portion of the slider 5 with the guide rail 6 is small.